Probing the non-thermal physics of stellar bow shocks using radio observations

Autores
Martinez, Javier Rodrigo; del Palacio, S.; Bosch Ramon, V.
Año de publicación
2023
Idioma
inglés
Tipo de recurso
artículo
Estado
versión publicada
Descripción
Context. Massive runaway stars produce bow shocks in the interstellar medium. Recent observations revealed radio emission from a few of these objects, but the origin of this radiation remains poorly understood. Aims: We aim to interpret this radio emission and assess under which conditions it could be either thermal (free-free) or non-thermal (synchrotron), and how to use the observational data to infer physical properties of the bow shocks. Methods: We used an extended non-thermal emission model for stellar bow shocks for which we incorporated a consistent calculation of the thermal emission from the forward shock. We fitted this model to the available radio data (spectral and intensity maps), including largely unexplored data at low frequencies. In addition, we used a simplified one-zone model to estimate the gamma-ray emission from particles escaping the bow shocks. Results: We can only explain the radio data from the best sampled systems (BD+43°3654 and BD+60°2522) assuming a hard electron energy distribution below ∼1 GeV, a high efficiency of conversion of (shocked) wind kinetic power into relativistic electrons (∼1 − 5%), and a relatively high magnetic-to-thermal pressure ratio of ηB ∼ 0.2. In the other systems, the interpretation of the observed flux density is more ambiguous, although a non-thermal scenario is also favoured. We also show how complementary observations at other frequencies can allow us to place stronger constraints in the model. We also estimated the gamma-ray fluxes from the HII regions around the bow shocks of BD+43°3654 and BD+60°2522, and obtained luminosities at GeV energies of ∼1033 erg s−1 and 1032 erg s−1, respectively, under reasonable assumptions. Conclusions: Stellar bow shocks can potentially be very efficient particle accelerators. This work provides multi-wavelength predictions of their emission and demonstrates the key role of low-frequency radio observations in unveiling particle acceleration processes. The prospects of detections with next-generation observatories such as SKA and ngVLA are very promising. Finally, BD+43°3654 may be detected in GeV in the near future, while bow shocks in general may turn out to be non-negligible sources of (at least leptonic) low-energy cosmic rays.
Fil: Martinez, Javier Rodrigo. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomía; Argentina
Fil: del Palacio, S.. Chalmers University of Technology; Suecia
Fil: Bosch Ramon, V.. Universidad de Barcelona; España
Materia
radiation mechanisms: non-thermal
radiation mechanisms: thermal
Astrophysics - High Energy Astrophysical Phenomena
radio continuum: general
Nivel de accesibilidad
acceso abierto
Condiciones de uso
https://creativecommons.org/licenses/by-nc-sa/2.5/ar/
Repositorio
CONICET Digital (CONICET)
Institución
Consejo Nacional de Investigaciones Científicas y Técnicas
OAI Identificador
oai:ri.conicet.gov.ar:11336/271135

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network_name_str CONICET Digital (CONICET)
spelling Probing the non-thermal physics of stellar bow shocks using radio observationsMartinez, Javier Rodrigodel Palacio, S.Bosch Ramon, V.radiation mechanisms: non-thermalradiation mechanisms: thermalAstrophysics - High Energy Astrophysical Phenomenaradio continuum: generalhttps://purl.org/becyt/ford/1.3https://purl.org/becyt/ford/1Context. Massive runaway stars produce bow shocks in the interstellar medium. Recent observations revealed radio emission from a few of these objects, but the origin of this radiation remains poorly understood. Aims: We aim to interpret this radio emission and assess under which conditions it could be either thermal (free-free) or non-thermal (synchrotron), and how to use the observational data to infer physical properties of the bow shocks. Methods: We used an extended non-thermal emission model for stellar bow shocks for which we incorporated a consistent calculation of the thermal emission from the forward shock. We fitted this model to the available radio data (spectral and intensity maps), including largely unexplored data at low frequencies. In addition, we used a simplified one-zone model to estimate the gamma-ray emission from particles escaping the bow shocks. Results: We can only explain the radio data from the best sampled systems (BD+43°3654 and BD+60°2522) assuming a hard electron energy distribution below ∼1 GeV, a high efficiency of conversion of (shocked) wind kinetic power into relativistic electrons (∼1 − 5%), and a relatively high magnetic-to-thermal pressure ratio of ηB ∼ 0.2. In the other systems, the interpretation of the observed flux density is more ambiguous, although a non-thermal scenario is also favoured. We also show how complementary observations at other frequencies can allow us to place stronger constraints in the model. We also estimated the gamma-ray fluxes from the HII regions around the bow shocks of BD+43°3654 and BD+60°2522, and obtained luminosities at GeV energies of ∼1033 erg s−1 and 1032 erg s−1, respectively, under reasonable assumptions. Conclusions: Stellar bow shocks can potentially be very efficient particle accelerators. This work provides multi-wavelength predictions of their emission and demonstrates the key role of low-frequency radio observations in unveiling particle acceleration processes. The prospects of detections with next-generation observatories such as SKA and ngVLA are very promising. Finally, BD+43°3654 may be detected in GeV in the near future, while bow shocks in general may turn out to be non-negligible sources of (at least leptonic) low-energy cosmic rays.Fil: Martinez, Javier Rodrigo. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomía; ArgentinaFil: del Palacio, S.. Chalmers University of Technology; SueciaFil: Bosch Ramon, V.. Universidad de Barcelona; EspañaEDP Sciences2023-12info:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://purl.org/coar/resource_type/c_6501info:ar-repo/semantics/articuloapplication/pdfapplication/pdfhttp://hdl.handle.net/11336/271135Martinez, Javier Rodrigo; del Palacio, S.; Bosch Ramon, V.; Probing the non-thermal physics of stellar bow shocks using radio observations; EDP Sciences; Astronomy and Astrophysics; 680; 12-2023; 1-140004-6361CONICET DigitalCONICETenginfo:eu-repo/semantics/altIdentifier/url/https://www.aanda.org/10.1051/0004-6361/202347720info:eu-repo/semantics/altIdentifier/doi/10.1051/0004-6361/202347720info:eu-repo/semantics/openAccesshttps://creativecommons.org/licenses/by-nc-sa/2.5/ar/reponame:CONICET Digital (CONICET)instname:Consejo Nacional de Investigaciones Científicas y Técnicas2025-09-29T10:29:00Zoai:ri.conicet.gov.ar:11336/271135instacron:CONICETInstitucionalhttp://ri.conicet.gov.ar/Organismo científico-tecnológicoNo correspondehttp://ri.conicet.gov.ar/oai/requestdasensio@conicet.gov.ar; lcarlino@conicet.gov.arArgentinaNo correspondeNo correspondeNo correspondeopendoar:34982025-09-29 10:29:00.886CONICET Digital (CONICET) - Consejo Nacional de Investigaciones Científicas y Técnicasfalse
dc.title.none.fl_str_mv Probing the non-thermal physics of stellar bow shocks using radio observations
title Probing the non-thermal physics of stellar bow shocks using radio observations
spellingShingle Probing the non-thermal physics of stellar bow shocks using radio observations
Martinez, Javier Rodrigo
radiation mechanisms: non-thermal
radiation mechanisms: thermal
Astrophysics - High Energy Astrophysical Phenomena
radio continuum: general
title_short Probing the non-thermal physics of stellar bow shocks using radio observations
title_full Probing the non-thermal physics of stellar bow shocks using radio observations
title_fullStr Probing the non-thermal physics of stellar bow shocks using radio observations
title_full_unstemmed Probing the non-thermal physics of stellar bow shocks using radio observations
title_sort Probing the non-thermal physics of stellar bow shocks using radio observations
dc.creator.none.fl_str_mv Martinez, Javier Rodrigo
del Palacio, S.
Bosch Ramon, V.
author Martinez, Javier Rodrigo
author_facet Martinez, Javier Rodrigo
del Palacio, S.
Bosch Ramon, V.
author_role author
author2 del Palacio, S.
Bosch Ramon, V.
author2_role author
author
dc.subject.none.fl_str_mv radiation mechanisms: non-thermal
radiation mechanisms: thermal
Astrophysics - High Energy Astrophysical Phenomena
radio continuum: general
topic radiation mechanisms: non-thermal
radiation mechanisms: thermal
Astrophysics - High Energy Astrophysical Phenomena
radio continuum: general
purl_subject.fl_str_mv https://purl.org/becyt/ford/1.3
https://purl.org/becyt/ford/1
dc.description.none.fl_txt_mv Context. Massive runaway stars produce bow shocks in the interstellar medium. Recent observations revealed radio emission from a few of these objects, but the origin of this radiation remains poorly understood. Aims: We aim to interpret this radio emission and assess under which conditions it could be either thermal (free-free) or non-thermal (synchrotron), and how to use the observational data to infer physical properties of the bow shocks. Methods: We used an extended non-thermal emission model for stellar bow shocks for which we incorporated a consistent calculation of the thermal emission from the forward shock. We fitted this model to the available radio data (spectral and intensity maps), including largely unexplored data at low frequencies. In addition, we used a simplified one-zone model to estimate the gamma-ray emission from particles escaping the bow shocks. Results: We can only explain the radio data from the best sampled systems (BD+43°3654 and BD+60°2522) assuming a hard electron energy distribution below ∼1 GeV, a high efficiency of conversion of (shocked) wind kinetic power into relativistic electrons (∼1 − 5%), and a relatively high magnetic-to-thermal pressure ratio of ηB ∼ 0.2. In the other systems, the interpretation of the observed flux density is more ambiguous, although a non-thermal scenario is also favoured. We also show how complementary observations at other frequencies can allow us to place stronger constraints in the model. We also estimated the gamma-ray fluxes from the HII regions around the bow shocks of BD+43°3654 and BD+60°2522, and obtained luminosities at GeV energies of ∼1033 erg s−1 and 1032 erg s−1, respectively, under reasonable assumptions. Conclusions: Stellar bow shocks can potentially be very efficient particle accelerators. This work provides multi-wavelength predictions of their emission and demonstrates the key role of low-frequency radio observations in unveiling particle acceleration processes. The prospects of detections with next-generation observatories such as SKA and ngVLA are very promising. Finally, BD+43°3654 may be detected in GeV in the near future, while bow shocks in general may turn out to be non-negligible sources of (at least leptonic) low-energy cosmic rays.
Fil: Martinez, Javier Rodrigo. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomía; Argentina
Fil: del Palacio, S.. Chalmers University of Technology; Suecia
Fil: Bosch Ramon, V.. Universidad de Barcelona; España
description Context. Massive runaway stars produce bow shocks in the interstellar medium. Recent observations revealed radio emission from a few of these objects, but the origin of this radiation remains poorly understood. Aims: We aim to interpret this radio emission and assess under which conditions it could be either thermal (free-free) or non-thermal (synchrotron), and how to use the observational data to infer physical properties of the bow shocks. Methods: We used an extended non-thermal emission model for stellar bow shocks for which we incorporated a consistent calculation of the thermal emission from the forward shock. We fitted this model to the available radio data (spectral and intensity maps), including largely unexplored data at low frequencies. In addition, we used a simplified one-zone model to estimate the gamma-ray emission from particles escaping the bow shocks. Results: We can only explain the radio data from the best sampled systems (BD+43°3654 and BD+60°2522) assuming a hard electron energy distribution below ∼1 GeV, a high efficiency of conversion of (shocked) wind kinetic power into relativistic electrons (∼1 − 5%), and a relatively high magnetic-to-thermal pressure ratio of ηB ∼ 0.2. In the other systems, the interpretation of the observed flux density is more ambiguous, although a non-thermal scenario is also favoured. We also show how complementary observations at other frequencies can allow us to place stronger constraints in the model. We also estimated the gamma-ray fluxes from the HII regions around the bow shocks of BD+43°3654 and BD+60°2522, and obtained luminosities at GeV energies of ∼1033 erg s−1 and 1032 erg s−1, respectively, under reasonable assumptions. Conclusions: Stellar bow shocks can potentially be very efficient particle accelerators. This work provides multi-wavelength predictions of their emission and demonstrates the key role of low-frequency radio observations in unveiling particle acceleration processes. The prospects of detections with next-generation observatories such as SKA and ngVLA are very promising. Finally, BD+43°3654 may be detected in GeV in the near future, while bow shocks in general may turn out to be non-negligible sources of (at least leptonic) low-energy cosmic rays.
publishDate 2023
dc.date.none.fl_str_mv 2023-12
dc.type.none.fl_str_mv info:eu-repo/semantics/article
info:eu-repo/semantics/publishedVersion
http://purl.org/coar/resource_type/c_6501
info:ar-repo/semantics/articulo
format article
status_str publishedVersion
dc.identifier.none.fl_str_mv http://hdl.handle.net/11336/271135
Martinez, Javier Rodrigo; del Palacio, S.; Bosch Ramon, V.; Probing the non-thermal physics of stellar bow shocks using radio observations; EDP Sciences; Astronomy and Astrophysics; 680; 12-2023; 1-14
0004-6361
CONICET Digital
CONICET
url http://hdl.handle.net/11336/271135
identifier_str_mv Martinez, Javier Rodrigo; del Palacio, S.; Bosch Ramon, V.; Probing the non-thermal physics of stellar bow shocks using radio observations; EDP Sciences; Astronomy and Astrophysics; 680; 12-2023; 1-14
0004-6361
CONICET Digital
CONICET
dc.language.none.fl_str_mv eng
language eng
dc.relation.none.fl_str_mv info:eu-repo/semantics/altIdentifier/url/https://www.aanda.org/10.1051/0004-6361/202347720
info:eu-repo/semantics/altIdentifier/doi/10.1051/0004-6361/202347720
dc.rights.none.fl_str_mv info:eu-repo/semantics/openAccess
https://creativecommons.org/licenses/by-nc-sa/2.5/ar/
eu_rights_str_mv openAccess
rights_invalid_str_mv https://creativecommons.org/licenses/by-nc-sa/2.5/ar/
dc.format.none.fl_str_mv application/pdf
application/pdf
dc.publisher.none.fl_str_mv EDP Sciences
publisher.none.fl_str_mv EDP Sciences
dc.source.none.fl_str_mv reponame:CONICET Digital (CONICET)
instname:Consejo Nacional de Investigaciones Científicas y Técnicas
reponame_str CONICET Digital (CONICET)
collection CONICET Digital (CONICET)
instname_str Consejo Nacional de Investigaciones Científicas y Técnicas
repository.name.fl_str_mv CONICET Digital (CONICET) - Consejo Nacional de Investigaciones Científicas y Técnicas
repository.mail.fl_str_mv dasensio@conicet.gov.ar; lcarlino@conicet.gov.ar
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